Key Definitions•Data model–A formal way of representing the data that are used and created by a business system–Shows the people, places and things about which data is captured and the relationships among them•Logical data model(our focus)–Shows the organization of data without indicating how it is stored, created, or manipulated3Key Definitions•Physical data model–Shows how the data will actually be stored in databases or files•Normalizationis the process analysts use to validate data models•Data models should balancewith process models4

What Is an ERD?•A picture showing the information created, stored, and used by a business system•Entities generally represent similar kinds of information•Lines drawn between entities show relationships among the data5An ERD ExampleEntityRelationshipAttributesIdentifier6

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Reading ERD•DOCTOR is scheduled for APPOINTMENT, APPOINTMENT includes DOCTOR•PATIENT schedules APPOINTMENT, APPOINTMENT is scheduled by PATIENT•APPOINTMENT generates BILL, BILL is generated by APPOINTMENT•PATIENT makes PAYMENT, PAYMENT is made by PATIENT•INSURANCE COMPANY insures PATIENT, PATIENT is insured by INSURANCE COMPANY•INSURANCE COMPANY makes PAYMENT, PAYMENT is made by INSURANCE COMPANY•BILL is paid by PAYMENT, PAYMENT pays BILL7Using the ERD to Show Business Rules•Business rules are constraints that are followed when the system is in operation•ERD symbols can show when one instance of an entity must exist for an instance of another to exist–A doctor must exist before appointments for the doctor can be made8

Using the ERD to Show Business Rules•

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